System for distinguishing between pulses having different characteristics



July 24, 1951 l ATWOQD 2,561,772

SYSTEM FOR DISTINGUISHING BETWEEN PULSES HAVING DIFFERENTCHARACTERISTICS Filed Oct. 6. 1944 2 Sheets-$heet l INVENTOR. JOHN B.ATM 00D BY 7%/WM/ A TTOANEY July 24, 1951 J. B. ATWOOD 2,551,772

7 SYSTEM FDR DISTINGUISHING BETWEEN PULSES HAVING DIFFERENTCHARACTERISTICS 2 Sheets-Sheet 2 Filed Oct. 6, 1944 rk/ggie 0200/;

ON pas/ms- 0F- FREEDOM Fig. 2.

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AS IN Hg 1 INVENTOR. JOHN B. A TWOOD A TTORNEV Patented July 24, 1951SYSTEM FOR DISTINGUISHING BETWEEN PULSES HAVING DIFFERENT CHARAC-TERISTICS Radio (Borporation of of Delaware America, a corporationApplication October 6, 1944,?Serial*No."557,524-

'This invention-relates toa mthodofand apparatusfor distinguishingbetween pulses-ornitferent amplitudes and/or different slopes;

The'invention, though not-limited-thereto 'fi'nds application "in apulse communicationreceiver' wherein it is desired-to 1 discriminatebetween desired incoming signal pulses and interfering pulses. Theseinterfering pulses may be signals from-undesired sources. The inventionalso is useful in laboratory apparatus where pulse separationon anamplitudeor Slope basis'i'sdesired.

Anobject of the present invention is to enable the elimination of"interfering pulses" whichareofhigher or lower amplitude than the desiredpulses; t

Another object is to 'enable the elimination "of interfering pulseswhich have different slopes than the desired pulses;

further'o'bj ectis to provide apparatus capable of separating pulses ofinherent amplitudes and/or-differentslopes;

Inaccordancewiththe invention; there is'provided a circuit arrangementcomprising two space discharge paths so" arranged that a signal pulse ofdesired amplitudeis permitted to pass through onepath andlater-utilized," while an interfering pulse of greater amplitude ispermittedtt'o pass through both p'athsfandthen cancelled or bucked out;These two space discharge paths may be in the form of diiierent electrondischarge device electrode structures which are normallynon.coni:lu'ctive and differently biased sothat they becomecondu'ctive'at different input potentials. If the interfering "pulse is of smalleramplitude-than the desiredfpulse, the'bi'as is so adjusted that only thedesired pulse passes through one i path so as" to "be 'laterutilized',while the interfering pulse'is' notipermitted' to pass through eitherpath.

"In order to discriminateibetween"desired and. undesired pulses "havingsubstantially thesame amplitude but having difierent slopes,theinventionmakes use of ap'lurali'ty ofcliiie'rentiator circuits andother elements for converting the pulses of different slopes to113111865 of different amplitudes. 'A fter thepulseshave been givendifferent amplitudes, they are-separated by suitably'ad'j'usting thebiases "on the 'elect'ronldi'schargedevicesorthe system.

*A"-more detailedflescription ofth'e invention follows inconjunctioniwithiia drawing, wherein:

Figs. 1;2? an'd."3i'llustrate three difier'ent? lembodiments 'of "theinvention'ior separating; pulses on-anemphtudeand/orslopebasis Referringto 1., ."there isi 'shown...an linput 5 are 'provide'd evacuatedelectron discharge do cuit elements for separating the desired from-theundesired" pulses. Terminal '1: may be" connected to a receiver(not'gshownf or any othersuitable source which-suppliespu1sesof*positive polarity of difierent amplitudes a'nd/ordifrerentslopes to this terminal. Vacuum tube fl's'erves'toarnplifythe"pulses applied to terminal 'I and-"toinvert'the polarity ofthe" appliedpulses from a positive 'to 151 a negative sign. The controlgrid'oftube4. 1sconnected through a resistance 3to -a;=potentiometer 21, whichserves to supply an adjustable bias to the control grid of the tube.Output pulses ofnegative polarity are taken from the anode 0'1 2'0vacuum tube -"4* and pass through the primary winding of anironcore'pulse transformer 28;

This transformer inverts the' polarity of the neg ative pulses appearing'in the primary winding" andsupp'lies positive pulses to' thecontrolgridsof screen grid vacuum tubes 9 and I0 'which'are connected inelectrically parallel'relaton to the secondary winding of 'transformer28 through condensers 5 andl respectively; The control grids-of tubesHand (0 obtain abiasthroughte- 30 sistor's 'fi and'il; respectively,from a potentiometer 25* across whose'terminals there is connected '2.

common bias battery 48; Tubes 9 and lfl'ar'e' preferably of asharp-cut-offtype'and are differentially'bia'sedby means of battery llin the cathode" circuit of tube '91 It should be u'nd'e'rstood thatbatteryI'Fshowsonly 'one Way of obtaining a differential bias and thatthe inven" tion is not limited to thiscircuit' detail since, if

desired, a difiere'ntial bias may be obtained/for g ex'ample, bydirectly grounding the cathode of,

tube "9 and obtaining'a' grid bias for thistube through resistor 6 fromanother potentiometer which can be connected acrossbatterylll.

The'anodes of tubes Band lll'are c'on'nectedto 5 opposite terminals of apotentiometer l2 which has a suitable positive. polarizingrpotentialconnected to a point intermediate its lengththrough resistor 50 and avariable tap 5| The potentlom eter i2 thus permits-the gain of the two.tubes 504i and ID to be differentially adjustedby D1Y0-,

vicling different anode loads for the tubes. The condenser l3 positionedacross the terminalsoi' potentiometer i2: is arranged so as "to equalizethee phase shift between the two sides oil-the l circuit. 7 In effect,this condenser enables: the-time andcondenser l3 are ;adj usted,;.;th isadjustment;

will hold for a large range of amplitude of the interfering pulses. Thebest adjustment is slightly different for very high amplitudes than i";

for lower amplitude pulses. Qutputfrom tubes 9 and I is in the form ofnegativelpulsesh Negative pulses from the anodes of tubes 9 and H! areapplied to the grids of triode vacuum tube amplifiers I8 and I9(operating classA) through condensers I l and It, respe'ctively.'lhegrids of tubes I8 and iii are connected through resistors I and ll,respectively, tothenegative ter-- This battery is shunt- I ed by aby-pass condenser, as shown. Condenser minal of a bias battery 52.

I4 and resistor l5 form differentiator circuit. Condenser l6 and.resistorl'lgalso form a. diiierentiator circuit. Thetubes l8 and I9serve to invert the polarity of the pulses applied to their grids andsupply positive pulses from their an-' odes to the primaries of thepulse transformers 20 andZi. The secondary-of transformer 29 isconnected so as to produce negative pulses in lead:53, while thesecondary of transformer 23 is reversed relative tothat of transformer2t so as to produce positive pulses in the same lead.

The secondaries of transformers 20 and 2t are and the re-.

connected together through lea sultant voltage appearing therein appliedthrough condenser 22 to the control grid of the output screengrid'vacuum tube 24.. The cute put of tube 24 appears as negative pulsesat terminalZfi. 1

sI-n the operation of the system ofFig. l, for separating desired fromundesired pulses, the differential: bias of battery H'ispreferably madeto be nearly equal to the anode current cut-off biasoitube 9. JIhecommon bias through 130-- tentiorneter 25 is made, to be large enough tomaintain tubes 9 and ill well below the anode current cut-off condition,the exact value. of this common bias depending upon the amplitude ofthe-pulses applied to the grids of these tubes. From an inspection ofthe drawing it will be evident that thetube 9 is given agreater biasthan thetube lfl so that there isrequired a pulse of greater magnitudeto be applied to tube 9 in order to pass through this tube than throughtube iii.

, Inorder to discriminate between pulses of different'l'amplitudes, thecircuit adjustments are so madelthat the desired signal pulse ispermitted to 'pass through only one side of the circuit;

namely only through tube It! and not through tube 9. Pulses of greatermagnitude than a desired pulse, such as interfering pulses, will passthrough both sides of the circuit; namely through both tubes 9 and I9,and will cancel or be bucked out in th e outputs of transformers 29 and2M Interfering pulses of smaller magnitude than that of the desiredsignal pulse will not pass through either tube 9for Iii.

Let us assume first that a single positive pulse oflow amplitude isapplied to the grids of tubes 9 and, iil through tube 4 and this pulseis insufficie nt to overcome the negative bias on the grids of tubes9fland Iii. Due to the greater negative bias'supplied from potentiometer2 5, it will .be seenthat there will be no output pulse in the anodecircuit of either tube 9 or It. Now if this single'p'osi'tive pulse oflow'amplitude in the input circuits of tubes 9 and I0 is gradually in:creased in amplitude, a point Will be reached 4 where a pulse willappear in the output of tube lil but not in the output of tube 9, due tothe differential bias supplied by battery II. This pulse which appearsin theoutput of tube ill will pass through tubes i9 and 24 and appear inoutput terminal 2 6. If, howeventhe: amplitude of the pulse applied tothe-grids of tubes 9 "and i9 is increased still further, to a magnitudesuffrj'zcient to overcome the negative bias of tube 9, a pulse willappearin the outputs of both tubes 9 arid iii and the. secondaries oftransformers 2G and 2 I. Underthiscondition, if the gain through the twosides of the circuit composed of tubes 9 I and" ill is adjusted bypotentiometer l2 and the and gl will cancel or buck each other and phaseshift adjusted by condenser l3, then pulses in the secondary windings oftransformers 2i] nothing' will appear in the output of tube 24. Thisadjustment will not affect the operation of the system at loweramplitudfis.

Condenser-resistor circuits 5, t, and l, 8 in the inputs of tubes 9 andID are difierentiator eir-, cuits. Condenser-resistor circuits I it and,'3;- l'! in the outputs of tubeslfi and I 9 are also differentiatorcircuits. These differentiating cir-fl. cuits are given short timeconstants andv aid separating pulses of a substantially equal ampl tudesand of different, slopes. It is known inthe. art that the voltageappearing across the resistor"; of an R.-C. differentiating circuit isproportional. to the slope of an applied voltage pulse. The. leadingedge of this applied voltage pulse can be represented at least to afirstv approximation by. theexpressionf Voltage e =kt, where k is theslope; and t the time. This principle is utilized in the. presentinvention to separate pulses of different slopes. v

In a system wherein it is desired to separate pulses on an amplitude andslope basis,.the following seven conditions may be encountered. Undereach one of these conditions, a description is given of the waythepulses can be separated or distinguished in the systemof Fig.1. ,In the.following description the undesired interfering. pulse is represented bythe letter U, While the desired or signal pulse is represented by thelet ter S. l. U is higher in amplitude than Sand of the, same slope atthe grids of tubes 9 and). U will pass through both tubes 9 and Illandbe cancelled or bucked out in the outputs of trans formers 2B and 2|.8 will pass through tube Ill. only and will be amplified in tubes I9 and24 and appear at output terminal 25. 1

2. U is lower in amplitude than Sand o f the' same slope at the grids oftubes 9 and'IO.. U. cannot go through either tube 9 or ID becauseitsamplitude is insufficient to overcome the common bias potential suppliedby potentiometer 25.. S. will pass through tube [0 and will be amplifiedin tubes 99 and 24 and will appear at output ter-. minal26.'

3. U and S are the same or almost the samein amplitude and of the sameslope at the grids of I tubes 9 and H]. In this condition, it isimpossible.

to eliminate U within a small range of voltages. This small percentagerange of voltages in which U and S cannot be separated can be reduced byamplifying the voltages of U and S before their application to tubes 9and I0, and then increasing the .bias applied by potentiometer 25, so asto; distinguish between the different pulses applied to tubes 9 and 10in a manner described above. in connection with the above conditions 1and 2. It should be understood that although the actual voltage range isconstant, the percentage range (ctr-applied lvoltagelt-l is: reducedwith. increased J amplltudei 4. :U and S are of. l the .same amplitude.but S isisteeper rinislope iati'thes grid 'ofrtubeqflx By virtue of thedifferentiating action ofcthettransformer 2B and circuits 5,16 and l, 8,the amplitude of'S will be higherith'an that ofU on the grids of vtubes- 9 and 10. By "adjusting potentiometer 25,1 itis pos'sible toprevent U from passing through either tube 9 or I 0, in the mannerdescribed above.- in connection with "icondition'2, while permitting Sto'pass throughtube l0."

*5; U0 and 1 S *are ofrthesame amplitude but. U

is'steeper. in slopeatthe grid ofutubewh: U will now. have "a greaterx'amplitude *on the grids of The: adjustment of potentiometer 25 enablesa suitable adjustment inathe bias .of the two tubes 9 and It sothatthiscondition can be fulfilled. It should be noted at this time thatsubsequent tothe difierenti'ating action the separation of the pulsesfollows substantially :condition 1.

6.: U i's of lower-amplitude than S :but of steeper slope-at the grid oftube 4. By adjusting the grid biasso'f'the tube 4 by meansofpotentiometer '21, it -i's' possible to eliminate U'and prevent it frompassing through :tube 4; If. this were not done, U and S might appearonthe grids of. tubes 9 and ID as pulsesuof. the same amplitude; which is:a condition" it is desired to avoid. l 7. S is of lower amplitude thanU but of steeper slopecat' the grid ofttuoe 4. Thelamplitudeof S' willIce-raised with respect to. U by .-virtue of the differentiating actionof thetran'sform'er wand thecircui-ts of 5, 16, and 1, 8. Potentiometer'25 isnow adjusted so as to permit Ufand S. to].

passwonly throughthe-tube It. Due to the differen tiatingactionofcondenser. l6, resistorll, and transformer 2 l., the amplitude of thesteeper sloped pulse Swill now' be higher than the amplitudeof U in the'output-ofritransformer 21 By adjusting the bias: onvpotentiometer 39.in. the input circuit of tube 24, it is now possibleto remove oripreventU from passin'g the tube while permitting. Satopass through this tube.

Another embodiment. of the system is: shown iI1" Fig .?2 which toperates-.on a.=s1ight1y different 1 principle .from Fig." 1.' Tubes 9 and ID ofFig. 2 are" similar totubes- Band |o OfFig.'1. Potentiometer 25 andits:battery48 supplies a common. bias to the "control gridsof tubes 9 and'lll. Batteryql l in the cathodecircuit of tube 9 furnishes thedifferential bias. Positive pulses are applied. to the input terminal29.: It should benoted. that in .Figi2 the differentiating circuits ofFig. 1 l are'omitted. Theoutput'of tube 9 iscsupplied 1 toa triggercircuit 33' having one degree of 6180? tricalfstability. Morespecifically, the trigger citw cult-may betof any Well known type,preferablyaa system :havingtwo vacuum tubeelectrode structures whoseanodes andlgridsare resistively interconnectedin a regenerative fashion;This trigger. circuit-by ivirtue of a difference in bias. applied 9 tothe grids of its two electrode structures, is. of a sself-restoring-type:so that it: has wonlyone degree of freedom. Theoutput 'of nthetriggercircuit -33 "is. connected to the screen grid ;of-= pentodeavacuum tube32 whose vcontrol:grid is;

coi'rpledtolthe:output: ofmtu'be l0 throughspulse 175 transformer 35*.Tube32iis normally. biased .to cute'off andlrequiresl a positive pulsefrom the :secw ondaryrlwinding of. transformer 35. in order for it topass current. Terminal 36 is. the output .1 ;terminal in which appearthe desired signal pulses but not:the interfering or noise pulses Beforedescribing the operation of Fig.2,.it;" shouldbenoted that the positiveinputpulsesap: 1

plied toainput terminal 29 are inverted in polarity -by "the. tubes 9and [Use as to appearas negative;

pulsesonthe anodes of these tubes. Pulse transformer 35 invertsrthenegative pulse supplied to its primary winding and thus supplies apositive pu'l'seifrom its secondary windingto the control xggrid of.pentodeu32, of a magnitude sufiicient toii. overcome the normal biasonthe control grid and cause tubetbto pass current. Tube 32 supplies anegative pulse to the output terminal=36.. Trig.- gercircuit 33 servestoremove the screen voltage :iirom tube 32 andthus prevents thepassageof'f current through this tube whenever the trigger firesw In theoperation. of Fig. .2, let us assume that: low amplitude interferingpulses are supplied to .t-input terminal 2 9. of positive polarity butof in.-'-

sufilcient magnitude to overcome the bias sup-e1 plied totubes 9 andIll-by potentiometer 25. Una der" thiscondition; these-plow. amplitudenoise pulses will not affect either tube 9 or ID and :not.

Ibo-passed thereby. Asthe amplitude of theposia tive input pulseis-raised; a point will be reached 1 Where vacuum tuba In will pass thepulsetbut tube 8 will notpass the pulse by virtueofthedifferential biassupplied by battery II. The pas-m usage of a pulseathroughtube l 0 willcauseapositive pulse to appear on the control grid of-tube-- 32; asa-result of- Which a negative -pulse "will appear at the outputterminal-536.: Howeven-"if higher amplitude positive y pulses appear atthe iinput terminal 2990f .a magnitude suflicient to overcome thebiastsupplied by: potentiometer 2 5 it and xibattery l these pulseswill: pass through both tubes fi and-I'll and appear-as negative pulsesThe ,negative *pulse appearing in theoutput of tube 9 will fireor renderactivethetrigger circuit 33 which is ofrthe self-restoring type havingonly onedegreeof electrical stability The operation of trigger circuit33 from its stable to its active r .--state in= response-to thenegativeinput pulse from "tube 9 *will remove the screen" grid voltage from tube=32 and th'us prevent tube32 from passing current? Under this condition;the pulse passedbyytube 9 will notapp'ear at the output" in the-anode==circuits of these two tubes.

ter-minal i A disadvantage 'of Fig. 2 as-comparedto Fig. 1 lies "in the'fact'that the system'of Fig. 2 is 'not selective to pulses ordiiferentslopes. Further,

the outputlterminalfids ent invention which :issimilar to-the system ofFig l, EXCGlDtlfGl :the eliminationpftubes l8: and

l9 and -differentiator circuits 14,- l5 and I6, Fla Fig; 3 isasimplificati-on of the-systemof'Fig. l. :The same elementsappearing-inFig. 3 which appear in Fig.1 have beengiventhe same refer'encewnumerals; In'order .XtO simplify the draw ingg and overcomeduplication of l illustration; the transformer-:28 and-vacuum tube 4 'tothe left of? condensers :5 f and l and vacuum "tube 424 which Fig. 3shows another embodiment pfthe prestheseelements of Fig. 1 are connectedto Fig. 3 in I the same manner illustrated in Fig. 1.

The potentiometer 12 of Fig. 1 has been replaced by potentiometer H2 inFig. 3. This potentiometer HZ'in Fig. 3 varies the screen voltagesof'tubes 9 and H1 in order to adjust the gains ofz: the two sides of thecircuit. The secondary windings of transformers 20 and M in Fig. 3 arereversed relative to the equivalent connections in Fig;1', in order toobtain pulses of proper polarity tobe applied to the tube 24.

"A. disadvantage of. Fig. 3 which is overcome by Fig. 1' is that it isnot possible to separate the undesired pulse from the desired pulse forall slope conditions. For example, the system of Fig. 3 cannot'separatepulses discussed in condition '7 above, where S is of lower amplitudethan U, but is of steeper slope at the grid of tube 4.

What is claimed is:

1. The method of separating pulses of different 7 slopes and ofsubstantially the same amplitude which includes the steps of convertingthese tially the same amplitude and of difierent slopes Which includesthe steps of differentiating these pulses to-produce pulses of the samepolarity but of different amplitudes, applying said pulses of difierentamplitudes to a pair of differentially 8 I trodes,"individualtransformers having theiryprimary windings coupled to the outputelectrodes of said structures, and a utilization circuit coupled inparallel to the'secondary windings of said transformers, saidtransformers being so poled as to produce pulses of opposite polaritiesin their secondary windings, and a pulsedifierentiator circuit betweenthe primary Winding of each transformer and the output electrode of itsassociatedi vacuum tube electrode structure. 5. Asystem for separatingpulses having dif- I ferent characteristics comprising axpai'r ofvacuum'tube electrode structures, each having an input electrode anda'n-outputielectrode, one or;. more sources of unidirectional potentialcoupled to said input electrodes for biasing the input electrodes to arelatively different degree, a cir-' cuit for'supplying said pulses tosaid input electrodes in cophasal relation, a. potentiometer for varyingthe relative gains of said pair of electrode structures, individualtransformers coupled to the output electrodes of said structures, and autilization circuit coupled in parallel to the output windings of saidtransformers, said transformers being so poled as to'produce'pul'ses ofopposite polarities in their output windings. 6. A system for separatingpulses having dif-" ferent characteristics comprising a pair of vacuumtube electrode structures, each having an input electrode and an outputelectrode, one or more sources of unidirectional potential coupled tosaid input electrodes for biasing the input electrodes to a relativelydifierent degree; a circuit for biased space discharge paths, adjustingthe biases of said paths so that pulses of a desired ampli-i tude passonly through the path havingthe smaller bias, while pulses whoseamplitude is smaller than said desired amplitude cannot pass througheither path and pulses of larger amplitude pass through both of saidpaths, and cancelling those pulses of larger amplitude after they havepassed through both of said paths.

3. A system for separating pulses having different characteristicscomprising a pair of vacuum tube electrode structures, each having aninput electrode and an output electrode, one or more sources ofunidirectional potential coupled to said input electrodes for biasingthe input electrodes to a relatively different degree, a circuit forsupplying said pulses to said input electrodes in cophasal relation,said circuit including a pulse differentiator for each of said inputelectrodes, individual transformers coupled to the output electrodes ofsaid structures, and a utilization circuit coupled in parallel to theoutput windings 01" said transformers, said transformers being so poledas to produce pulses of opposite polarities in their output windings.

4. A system for separating pulses having different characteristicscomprising a pair of vacuum tube electrode structures, each having an,input electrode and an output electrode, one or supplying said pulses tosaid input electrodes in cophasal relation, a potentiometer across theout-' put electrodes of said pair of electrode structures, saidpotentiometer having a variable tap supplying polarizing potentials tosaid outputelectrodes, and a variable condenser across saidpotentiometer for equalizing the time constants of the output circuitsof said pair "of electrode structures, individual transformers havingtheir input windings coupled to the output electrodes of said structuresthrough another-pair of electrode structures, and a utilization circuitcoupled in parallel to the output windings of said transformers, saidtransformers being so poled as to produce pulses of opposite polaritiesin their output windings.

'7. A system for separating pulses having different characteristicscomprising a pair of vacuum tubes each having a grid, a cathode and ananode, an electrical connection between said grids for coupling saidgrids in parallel relation, an iron core transformer having a, primarywinding coupled to a source of 'said pulses and a secondary windingcoupled to said electrical connection for supplying pulses in cophasalrelation to said grids, one or more sources of potential fordifferentially biasing said grids, individual transformers'having theirprimary windings coupled through individual differentiator circuits tothe I anodes of said tubes, said last: transformers being so poled as toproduce pulses of opposite polarities in their secondary'windings, autilization circuit coupled in parallel relation to said secondarywindings, a potentiometer connected across said anodes, and means incircuit with said potentiometer for equalizing the phase shifts of energpassing through said tubes.

8. A system for separating pulses having different characteristicscomprising a pair of vacuum tube electrode structures, each having aninput electrode, a screen'grid and an output elecj trode, one or moresources of unidirectional po- 1) tential coupled to said ridsrt'rbiasing the grids relatively differentdegree, a circuit for p ingjsaidpulses to said: inputelectrodes irr coformers havingtheipinputwndings coupled to the output elebtrodes' oi" structures, and autilization circuit couplcdisin, parallel to theJout-i out, windings of,said; transformers, said iitransformers being so poled as to produce pues of posite polarities in their output windings.

9. A system for distinguishing between pulses having differentcharacteristics, comprising a pair of vacuum tube electrode structureseach having an input circuit and an output circuit, means for biasingsaid input circuits differently, means for applying said pulses to bothof said input circuits in electrically parallel relation, a utilizationcircuit coupled to the output circuit of that one electrode structurewhich has the smaller bias applied to its input circuit, and meansresponsive to pulses of a magnitude sufiicient to pass through bothelectrode structures for eliectively interrupting the coupling path fromsaid utilization circuit to the output circuit of said one electrodestructure.

10. A system for distinguishing between pulses having difierentcharacteristics, comprising a pair of vacuum tube electrode structureseach having an input circuit and an output circuit, means for biasingsaid input circuits differently, means for applying said pulses to bothof said input circuits in electrically parallel relation, a utilizationcircuit coupled to the output circuits of that one electrode structurewhich has the smaller bias applied to its input circuit, and meansresponsive to pulses of a magnitude sufiicient to pass through bothelectrode structures for effectively interrupting the coupling path 4.

from said utilization circuit to the output circuit of said oneelectrode structure, said means including a self-restoring electrondischarge device trigger circuit coupled to the output circuit of thatelectrode structure which has the larger bias applied to its inputcircuit.

11. A system for separating pulses having different characteristicscomprising a pair of screen grid vacuum tubes each having a grid, acathode and an anode, an electrical connection between said grids forcoupling said grids in parallel relation, an iron core transformerhaving a primary winding coupled to a source of said pulses and asecondary winding coupled to said electrical connection for supplyingpulses in cophasal relation to said grids, one or more sources ofpotential for difierentially biasing said grids, a second pair of vacuumtubes having their inputs coupled to the anodes of said first pair oftubes, a differentiator circuit for the input of each tube of saidsecond pair, individual transformers having their primary windingscoupled to the outputs of said second pair of tubes, said lasttransformers being so poled as to produce pulses of opposite polaritiesin their secondary windings, and a utilization circuit coupled inparallel relation to said secondary windings.

12. A system for separating pulses having different characteristicscomprising a pair of vacuum tube electrode structures, each having aninput electrode and an output electrode, one or more sources ofunidirectional potential coupled to said input electrodes for biasingthe input electrodes to a relatively difierent degree, a circuit forsupplying said pulses to said input electrodes F0- in cophasal relation,a potentiometer for varying he slative ains s id-pa red electrodestructures, individual transformers coupled .togthepute put electrodesof, said structuresthrough another pair of vacuum tube electrodestructures, and a utilization circuit coupledeintiparallel to therouteputjewindings oi said transformers, said transformers beings-o poledaSIQPI'QduQQ pll1SeS:0f,ODpG- sitespolaritiesin.thdirzmltpmt;windingsjf. g

;..l:3.. -.A. circuiuforidisoriminating betweenzreceived pulses ofvoltage in accordance with a characteristic thereof comprising, anelectron discharge device having current flow therein determined by theapplication of voltages thereto, a first diilerentiator circuit fordifferentiating received voltages pulses, a second difierentiatorcircuit for differentiating received voltage pulses, means including aphase shifting circuit, different paths from said differentiatorcircuits to terminals on said phase shifting circuit which are onopposite sides of the electrical center of the phase shifting circuit,and two branches coupled to said terminals and producing voltage pulsesof opposite polarities in response to current flow therein, andconnections from the output terminals of said branches to said electrondischarge device, whereby the flow of current in said device isdetermined by the voltage pulse in the output of at least one of saidbranches and the occurrence time of the pulses in the outputs of bothbranches. 14. The method of separating a desired pulse from an undesiredpulse when the desired pulse is of lower amplitude but of steeper slopethan the undesired pulse, which comprises differentiating said pulses soas to raise the amplitude of the desired pulse with respect to theundesired pulse, passing said differentiated pulses through a spacedischarge path, and increasing the amplitude of that differentiatedpulse representative of the desired pulse by a further dilferentiationprocess, whereby the desired pulse now has an amplitude higher than theundesired pulse.

15. The method of separating a desired pulse from an undesired pulsewhen the desired pulse is of lower amplitude but of steeper slope thanthe undesired pulse, which comprises differentiating said pulses so asto raise the amplitude of the desired pulse with respect to theundesired pulse, passing said differentiated pulses through a spacedischarge path, increasing the amplitude of that differentiated pulserepresentative of the desired pulse by a further difierentiationprocess, whereby the desired pulse now has an amplitude higher than theundesired pulse, and passing only the resulting higher amplitude desiredpulse through another space discharge path.

16. The method of separating pulses of different slopes and ofsubstantially the same amplitude which includes the steps of convertingthese pulses to pulses of different amplitudes, applying the pulses ofdiiierent amplitudes to a pair of paths, enabling pulses of apredetermined amplitude to pass through only one of said paths,preventing pulses of smaller amplitude from passing through either path,enabling pulses of larger amplitude to pass through both of said paths,but reversing the polarity of the pulse passing through one of saidpaths relative to that passing through the other path, and combiningsaid pulses of reversed polarities after they have passed through bothof said paths.

JOHN B. ATWOOD.

- (References on followi page) REFERENCES CITED 1 The followingreferences are of record in the fi1ej of this patent:

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